As the energy storage device, for example, an energy storage device including an electrolyte solution including a specific compound as an additive is known.
As this type of an energy storage device, for example, an energy storage device, in which an electrolyte solution includes an unsaturated sultone compound such as 1,3-propene sultone as an additive, is known (JP 4190162 B1).
In such an energy storage device, a degradation of an electric capacity can be suppressed even when the energy storage device is left under elevated temperatures since the electrolyte solution includes an unsaturated sultone compound.
However, in such an energy storage device, since the electrolyte solution merely includes an unsaturated sultone compound as an additive, a degradation in power performance of an energy storage device may not be necessarily adequately suppressed when the energy storage device is left under elevated temperatures or charged/discharged repeatedly under elevated temperatures.